Find text with mark and delete it

Assume we are constantly typing some text and directly behind it we have some text with some mark like a red color (let’s call that mark “color”). Now our cursor is directly at the boundary between the normal (black) text and the red one. Each time we type a new letter, a corresponding black letter gets inserted.

Now, we want to find the entire range of the red text (the cursor is supposed to be at the boundery between black and red text, if that matters) and, more importantly delete the red text.

Is there a good strategy to solve that issue and, if so, how?

Many thanks for your support in advance!